Characterization of Cutaneous Leishmaniasis Ulcers Utilizing a Multispectral Imaging System

Cutaneous Leishmaniasis (CL) is a parasitic disease caused by protozoan parasites of the genus Leishmania. The socioeconomic burden associated with CL has caused the disease to be responsible for 293,000 DALYs (Disability Adjusted Life Years) by 2019. CL produces ulcers that in most cases are misdiagnosed in primary health care units. CL is a disregarded tropical disease and it has been declared as a community health problem. However, CL lacks the development of novel tools that allow a better understanding of this illness. Multispectral imaging systems belong to the area of optical tools that allow the acquisition of diffuse reflectance data. Those systems measure the radiance reflected by a surface in a few wavelengths of the electromagnetic spectrum. Skin-biological parameters can be measured with these systems, by using mathematical models that can measure optical parameters that represent biological changes in tissue. Cutaneous illnesses, such as cutaneous cancer and melasma, have been analyzed by means of those systems. However, their use in CL has been limited. In this article, we propose the use of a three-layer diffuse reflectance model for the study of CL in two patients. Multispectral images were acquired, which were later processed by means of a direct-mathematical model and an optimization approach. As result, values of optical variables are obtained which are related to the following biological parameters: volumetric fraction of melanin, hemoglobin, oxygen saturation, diameter of keratinocytes, collagen, fibroblasts, and macrophages; as well as volumetric fraction of collagen. Some of these parameters show differences between ulcers in active and healing phases.